Though are cars are very different in many ways, it seems they have one thing in common...they both run on 5 cylinders.
Sorry to hear about your bad luck. I also have heard of the o-rings leaking on 603's. Do you have a good mechanic that you could take the car over to to have him listen to it? It would only cost a small fraction of what it costs to "throw" parts at the problem.
Good Luck
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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